Table 1 Baseline characteristics of patients

Age, mean (SD), years

32.7 (4.1)

32.4 (4.3)

0.001

BMI, mean (SD), kg/m²

22.9 (3.7)

22.8 (3.7)

0.094

Duration of infertility, median (IQR), years

3.0 (2.0–4.0)

3.0 (2.0–4.0)

0.832

Type of infertility, No. (%)

 Primary

1482 (56.9)

5894 (57.8)

0.412

 Secondary

1121 (43.1)

4299 (42.2)

Cause of infertility, No. (%) ^a

 Male factor only

771 (29.6)

2761 (27.1)

0.028

 Ovulation disorder

429 (16.5)

1623 (15.9)

 Tubal factor

891 (34.2)

3768 (37.0)

 Endometriosis

197 (7.6)

842 (8.3)

 Unexplained

315 (12.1)

1199 (11.8)

Basal FSH, median (IQR), mIU/mL ^b

6.4 (5.1–7.9)

6.3 (5.0-7.8)

0.581

Basal LH, median (IQR), mIU/mL ^b

3.5 (2.3–5.2)

3.6 (2.3–5.2)

0.319

Basal oestradiol, median (IQR), pmol/L ^b

152.0 (110.0-195.0)

152.0 (110.0-196.0)

0.917

AMH, median (IQR), ng/mL

2.6 (1.4–4.4)

2.5 (1.4–4.4)

0.317

FT4, median (IQR), ng/dL

1.3 (1.2–1.4)

1.3 (1.2–1.4)

< 0.001

TSH, median (IQR), mIU/L

2.2 (1.5-3.0)

2.0 (1.4–2.7)

< 0.001

Sperm concentration, median (IQR), million/mL

49.7 (24.9–85.2)

52.0 (26.5–86.6)

0.102

Sperm motility, median (IQR), %

28.0 (15.7–43.5)

29.0 (16.2–44.0)

0.227